Roughly 12.5 percent of the U.S. population, or 37.1 million people, moved to a new home, up from a low of 11.9 percent, or 35.2 million, in 2008, according to census figures released Monday.

While it was the first percentage gain in U.S. mobility since the height of the housing bubble in 2005, the levels remain at historic lows. Virtually all the new moves in 2009 also occurred within a county, indicating that most were renters and lower-income people going locally from job to job.

The share of longer-distance moves across counties and states was basically unchanged. That is evidence that college graduates and younger professionals were temporarily staying put during the housing crunch, rather than seeking out new careers in other regions of the country.

Analysts said the nation's low mobility could have social benefits if people feel they can rely more on long-time neighbors and family to get through hard times. But they cautioned that it could also stunt a fledgling economic recovery if talented new workers feel trapped.

"Communities with lower levels of mobility do have higher levels of trust and well-being, but they also have much less higher rates of productivity and innovation," said Richard Florida, a professor of U.S. urban theory at the University of Toronto. "I would err in a downturn on making sure people have economic opportunities."

The levels of people moving have been gradually declining for decades, more recently due to an aging baby boomer population that is less mobile, since hitting a peak of 21.2 percent in 1951. But the rate had generally leveled off around 13 to 14 percent before dropping sharply in 2008 due to the recession.

Most demographic groups saw a slowdown in U.S. migration, with the young and old taking the biggest hits.

About 1 in 4 adults ages 25-34 last year changed residences. That's up slightly from 2008 but down from 32 percent in 2000 as many held off on a job search, delayed marriage or opted to pursue an advanced degree in the current recession.

Older Americans also stayed put. Their overall mobility in 2009 was largely flat, registering at 3.4 percent for seniors 65 and older and 4.9 percent for pre-seniors ages 60-64. Long-distance migration for both groups fell to below 2 percent, the lowest in at least two decades, after most older people delayed retirement and kept working due to shriveled stock and home values.

Katherine Newman, a sociology professor at Princeton University, said she was worried that mobility may have decreased too sharply in recent years, noting that many young adults were being forced to "boomerang" back home to live with parents because of limited jobs.

"In many households where that move is not voluntary and is merely a reflection of financial distress, there can be a great deal of tension," she said.

The findings are the latest to highlight the social impact of the housing crunch and subsequent financial meltdown on U.S. population growth. The effects include renewed gains for large cities that had been losing residents to far-flung exurbs as well as losses for retirement destinations concentrated in the South and West.

There are also implications for the 2010 census, which will be used to distribute House seats and more than $400 billion in federal aid. Based on torrid Sun Belt growth earlier in the decade, states such as Arizona and Florida were on track to gain two House seats apiece before mortgage foreclosures began to wrack their economies. They now may lose out to the likes of California and New York, which could avert a loss of seats as they retain more big-city residents.

"Overall, there is nothing here that suggests a light at the end of the tunnel in the continued slowdown of long distance migration in the U.S.," said William H. Frey, a demographer at Brookings Institution who analyzed the numbers. "States and communities hoping to see renewed migration gains in college graduates, retirees and families as a spark to their economic growth will continue to be disappointed."

Other findings:

—The number of immigrants coming to the U.S. from other countries fell to 1.09 million, the lowest since 1995.

—Blacks, single people, high-school dropouts and the poor were among the most likely to move.

—The most commonly cited reasons for moving were housing-related, such as a desire to live in a better neighborhood; they represented 45.9 percent of movers. Other factors included family (26.3 percent) and jobs (17.9 percent).